Recently, the world’s major countries have begun to consider artificial intelligence (AI) as part of their national strategies. The widespread development of AI is changing our lives and ideas. In China, a small number of researchers have been concentrating their attentions onto the fundamental theory of intelligence based on dialectical materialism for more than 20 years, including the formation mechanism of intelligence, logical basis, mathematical foundation, coordination mechanism and contradiction transformation.At last, they set up the mechanism-based artificial intelligence theory, the universal logic theory, the factor space theory, the coordination theory, the extenics theory and the analysis of set pairs. The mechanism-based artificial intelligence theory is the general theory of intelligence based on the formation mechanism, it unifies the strucrualism, functionalism, and behaviorism, the existing three isolated major schools of artificial intelligence, into a harmonious unity, and makes the primary consciousness, emotion, and lntellect into a trinity; factor space theory is the mathematical foundation for mechanism-based artificial intelligence theory; universal logic theory is the logical based for mechanism-based artificial intelligence theory. In this paper, we introduces the basic theory and application of universal logic theory and clarifies its significance and value. Propositional universal logic (containing both hard and flexible logics) is based on “generalized probability theory”, and can be regarded as a proposition-level library of intelligent information processing operators. It contains all 18 flexible information processing modes (including 16 Boolean information processing modes). The operators are strictly expressed as <a,b,e>, so appropriate complete clusters of information processing operators can be identified. In each mode, different uncertainties are determined by the degree of encoding <k,h,β,e>, which connects with the direct operator required. Consequently, flexible information processing can considered to be a coded lock, with <a,b,e> + <k,h,β,e> as its passwords. Additionally, all of the passwords are saved in the library, thereby satisfying the demand for “one lock-one passwords”.